Process of cracking oil



NOV- 23 193? c. E. BEATIE y PROCESS 0F CRAGKING onJ Filed Julyv 3l, 1920Patented Nov. 23, 1937 arcata PATENT orties PROCESS F CRACKING OIL CecilE. Beatie, Forest Hills, N. Y., assigner, by

mesne assignments, to Power Patents Company, Jersey City, N. J., acorporation of Maine Application July 31, 1920, Serial No. 400,531

18 Claims. (Cl. 19649) This invention relates to a process of crackingoil and more particularly to a continuous process of cracking oil instages.

Since the decomposing or cracking temperatures of mineral oils orvarious distillates thereoi are usually higher than their boilingtemperatures, it is the common practice in cracking oils to place themunder sufficient pressure so that they may be raised to the decomposingtemperature before they are vaporized. When cracking oil under pressure,three factors, namely, pressure, temperature and time must be accuratelycontrolled in order to secure the best results. AIf a high temperatureis used for cracking, the oil must be subjected to such a temperaturefor only a short time. Conversely, if a low temperature is used forcracking, the oil must be held at such temperature for a long time.Either pressure-temperature combination will produce substantially thesame results but the higher temperatures are usually preferred becausewith them oil may be cracked more rapidly. When cracking oil cn acommercial scale, there is a critical temperature for each different oilabove which it is not practicable to go regardless of the time factor,because at these higher temperatures carbon is deposited so rapidly thatthe apparatus soon becomes clogged.

For every cracking temperature, each oil appears to have a criticallength of time, to which it may be subjected to such temperature beforeit will be broken down almost instantaneously into carbon and gases.With some oils, the point of fatigue or the point where the oil seems tosuddenly decompose may occur while the oil has a comparatively lowspecific gravity. If, however, the temperature and pressure to which theoil is being subjected are changed or if carbon is removed from the oil,the oil may be reduced to a comparatively high specic gravity withoutdanger of reaching the fatigue point.

The heavier hydrocarbons decompose more' easiy, that is, at lowertemperatures and pressures, than the lighter hydrocarbons, and thereforeit is desirable that oils of different gravities be decomposedseparately. When a hydrocarbon is cracked, a plurality of diiierenthydrocarbons are formed Whose specific gravities vary in series from thelow speciiic gravity up to the high specic gravity. The hydrocarbonshaving a specific gravity higher than that of gasoline or the desiredhydrocarbons are usually separated from the desired hydrocarbons bycondensation and returned to the still for retreatment. Thosecondensates having a specic gravity higher than gasoline preferablyshould not be mixed with the oil from which they are formed and returnedto the still to be again cracked, because a mixture would be formed forwhich it would be difficult to nd the proper combinations of pressure,temperature and time to obtain the most favorable cracking. withoutreaching the fatigue point.

The primary object of the present invention is to provide a process ofcracking oil by which the oil may be cracked in stages to allowintermediate decomposition products of the oil to be treated separately.

Another object of the invention is to provide a process of cracking oilin stages in which the residuum oil from one stage advances to asucceeding stage for treatment at a lower temperatureY and heaviercondensates of vapors formed in one stage advance to a preceding stageor in a direction countercurrent to the advance of the residuum.

Another object of the invention is to provide a continuous process ofcracking oil by which the various gravities of oil formed successivelyin the course of the heat decomposition processV may be crackedseparately under diierent conditions oi pressure and temperature.

Another object of the invention is to provide a process of cracking oilin stages by which the lighter or lower specific gravity constituentsare cracked in the stages maintaining the highest temperature andthecarbon and heavy residue are removed from the stage maintaining thelowest temperature.

Another object of the invention is to provide a process of cracking oilin stages by which the carbon which is formed in each of the stages iscontinuously and progressively carried forward through the stages to thepoint of discharge by a stream of fresh incoming oil advancingsuccessively through the stages.

Another object of the invention is to provide a process of cracking oilin stages by which the heavier condensates are separated from theiinished distilled residue and carbon formed in each stage and thesecondensates are progressively circulated through the various stages forretreatment therein under the proper conditions of pressure andtemperature.

Another object of the invention is to provide a process of cracking oilby which the pressure and temperature of the oil and the time the .oilis under predetermined pressures and temperatures may be accuratelycontrolled.

A further object'of the invention is to provide a process of crackingoil by which the deposition of carbon in the treating apparatus may beeffectively controlled.

With these and other objects in view, the invention consists in theimproved process of cracking oil hereinafter describedY and particularlydefined in the claims.

The process embodying the preferred forrn'ofY the invention ispreferablyY carried out in such a manner as to produce gasoline asarnisrhed :.iistillate.V The oil to be treated is preheated and forcedcontinuously under'pressure through a series of separate cracking coilsarranged in stages. The residuum of oil from one'stageV perature for itsnext treatment. 'Ihe residuum Y which is separated from the vapors ineach stage has its pressure'reduced and-passes to a surgeV tank whereYit is mixed withY a heavy condensate from a preceding or a succeedingstageY in accordance with the Vspeciiicgravity of lsuch condensate. Thismixture is then pumped under pressure through the cracking coil of thenext succeeding stage. The temperature and pressure of the oil as itpasses through each of the cracking coils is controlled to produce themaximum amount of gasoline, but this temperature varies in the stage inaccordance with the gravity of the oil being treated'` Forrthe lighteroils,V higher temperatures and pressures are used, and for the heavieroils, lower temperatures and pressures are used. YIn each of thecracking coils,

the maximum temperatures and shortest time Y intervals'are used whichwill give the highest yields with practicable operating conditions.

In the accompanying drawing is diagram-Y matically illustrated a nowsheet of a'process embodying the preferred form of the invention.

A process of cracking an oil such as crudeoil, kerosene, gas oil or fueloil to produce gasoline maybe carried out in the apparatus illustratedin the drawing as follows: Crude or gas oil from storage YHl ows'througha line l2 to a heat interchanger I4 and passes through aline I6 to asurge tank I8. From the surge tank Yi8 the oil is circulated fortreatment in the appalratus of a irst stage converter. The oil leavingthe surge tank I8 is placed under pressure by means of a pump 2! andforced through a cracking or heating coil 22 positioned in a furnace2Q.; The heated and vaporized oil leaves the coil 22 through a line 26and passes into a separator 28. Vapors separated from the oil in theseparator 28 ow through an offtake 3E! through aYpressure-reducing valve32 thence into the bottom of a spray condenser 34. In the condenser 34the vapors are subjected to a spray of heavy condensate which is takenfrom an overflow tank 36 by means of a pump 33 and Vpassed through acooling coil 652 to a spray nozzle s2 in the upper portion of thecondenser. The heavy condensate removes all of the heavier portions ofthe oil and the nished vapors flow through a line 4d to a condenser lwhere the vapors are condensed and the resulting conden'sate'passesthrough a line 43 to a storage tank SQ.

Y Theoil residuum collected in the separator 28,A passes through afloat-'controlled valve 52 to a line 54 and thence to a surgeV tank 5ewhich r Yl i2 into a spray condenser H4.

thecondenser f id are condensed by means of a Aheavy condensate which istaken from an overoil cracked in the coil E52 passes through a line 65to a second stagevapor separator 68. The vapors from the separator 53pass into an offtake 153 and ow through a pressure-reducing valve 'l2into a spray condenser 14. In the condenser lll the vapors are condensedby means of a heavy condensate which is taken from an overiiow tank l bymeans of a pump 78 and forced through a cooling coil 8@ to a spraynozzle 82 mounted in the Yupper portion of the condenser lll. The nisheddistillatevapors pass through a line 8f?- to a condenser 8e and thedistillate passes through a line 38 to a line 9U which conects with thefinished distillate line 5:8.

The oil'residuum from the second stage separator flows outrthrough afloat-controlled valve 92 through a line S4 to a surge Vor storageV inthe coil 32 passes through a line Eto a separator i538 which hassubstantially the same vconstruction as the separators 68 and 2S. The

vvapors from the separator M58 pass through an offtake i through apressure-reducing valve The vapors Vin flow tank Hand vcirculated bymeans ofra pump H3 through a cooling coil l2@ to a spray nozzle 22mounted' in the upper portion of the :condenser I I4. The nisheddistilled vapors from the condenser l id pass through a line 12e to aVcondenser i2@ and the distillate passes Vthrough a line i 28 which isconnected'with the iinished distillateline 9i). Y

' The residuum from therseparator m8 flows through afloat-controlledValve i313 to a line 32 and thence into the heat interchanger l fromYwhich it passes through a line 134 to a residuurn storage tank ill-5.

The heavy condensate condensed in the condenser 34! of the first stageconverter overflows from the tank 35 and passes through a line I to thesurge tank for the third stage converter. A. line M23 may also beconnected between theline Hi8l andthe surge tank it by which the heavycondensate may pass to the surge !8 for retreatment in the first stageconverter. The heavy condensate recovered inthe condenser lllof thesecond stage converter overflows from the tank 'H5 and passes through aline M2 to the surge tank i3 for the first stage converter. A line Millmay also lee-connected between.Y the line l and the surge tank 5e bywhich the heavy condensate from the second stage converter may pass tothe surge tank 5S for retreatrnent. The heavy condensate Vfrom thecondenser l!!!Y of the `third stageV converter overflows from the tankH6 and passes through a line M5 to the surge tank 55 for the secondstage converter. A line MS may also be connected between the lino .i 136and the surge tank Se by which the heavy ment.

Withthe apparatus outlined above, the heavy condensates formed in thedifferent stages of the cracking may bey passed to a surge tank in apreceding or the same stage to be mixed with a residuum oil inaccordance with the specic gravity of the oil .to b-e treated and inaccordance with the specic gravity of the heavy condensate. In thepreferred form' of the invention, the main body of the oil or theresiduum remaining in the separators of the different stages advancesfrom the first to the third stage converters to be subjected toprogressively lower temperatures. The heavy condensates formed in thevarious stages, however, advance from the third to the rst stageconverters or in a countercurrent direction to the advance of the oil.All of the free carbon formed in the cracking operation is carriedforward continuously with the main body of the oil and is dischargedwith the residuum from the separator of the third stage converter, whichconverter is maintained at the lowest temperature. By this means thecarbon or residue is separated from the oil in the lower temperaturestage of the apparatus where the carbon is least liable to cause troublein the operation.

The cracking of oil in separate stages permits the various decompositionproducts of the oil to be grouped separately and treated separatelyunder the most favorable conditions of temperature and pressure. The oilmay be handled in each stage by a pump to accurately control the timeVperiod and therefore the higher tem'- peratures may be used bycirculatingr the oil at high velocities. The high velocity circulationoi stage converter.

the oil further assists in carrying residuum and carbon through theapparatus so that it will not become clogged and also serves to carrythe Vapcrs out of the heated Zone as soon as they are formed so that thevapors will not be supercracked. A sample of the oil being treated ineach of the converters may be removed to determine the amount of freecarbon in the oil and accordingly the three factors, time, pressure andtemperature used in the cracking coil of each stage converter may beaccurately regulated to obtain the desired nished distillate and themaximum evaporation or cracking. v

In the rst stage converter the freshy incoming fuel or gas oil iscirculated so rapidly through thecracking coil that the oil is notcracked to any appreciable extent but is merely topped or vaporized sothat the vapors may be fractionally condensed. The heavy condensatewhich is mixed with the fresh incoming oil, however, has resuited fromtwo previous heat treatments of oil and condensates in the third andsecond stage converters and receives another cracking treatment in thecoil of the rst stage converter. This mixture of crude oil andcondensate has the lowest specific gravity of any of the oil mixtures fwhich is to be treated and is subjected to the highest temperatures.

The oil treated in the second stage converter consists of the residuumof the rst stage converter and the heavy condensate from the third Theresiduum is subjected to a lower temperature andrpressure in the secondstage converter and is therefore further vaporized. The heavy condensatewhich has previously had a cracking treatment in the third stageconverter is given its second cracking treatment.

rIhe oil treated in the third stage converter consists of a mixture ofthe residuum from the second stage converter and the heavy condensateformed in the first stage converter. The residuurn being treated under alower temperature and pressure than that maintained in the second stageconverter is further vaporized.4 Any of the oilV passing through thecoil of tie third stage converter which has not been vaporized by thethird heat treatment in the third stage converter passes out oftheapparatus as a residuum which is controlled to be suitable for fuel cilpurposes. The heavy condensate of the mixture treated in the third stageconverter is given its rst cracking treatment in the second stageconverter.

Any oil which has not been vaporized in any of the various stages nevergoes through the same Y cracking or heating elements twice and thereforethe length of the time in which any particular portion of the oilremains under treatment may be accurately controlled to prevent the oilfrom reaching the fatigue stage or a point where it will be broken downwith an excess formation of carbon. The treatment of oil in each stageconsists of a finishing cracking operation to form a finisheddistillate, an intermediate cracking operation to form a heavycondensate, a cleaning or topping operation to form vapors for thefinished distillate and the heavy condensate, and the removal of carbonfrom the finished distillate and heavy condensate. ln each stage. thevapors formed are fractionally condensed to separately collect thefinished distillate and the heavy condensate. The carbon separated isdeposited in the residue to be advanced to a following stage and theheavy condensate free from carbon advances to a preceding stage.Although the heavy condensate may be mixed with a residue containingcarbon', it has a lower specific gravity than the oil mixture of thestage in which it was formed and is mixed with an oil which is subjectedto a different temperature and pressure than the temperature andpressure of the stage in which it was formed so that the operation doesnot tend to bring the oil towardV a fatigue point. On the other hand,the residue containing the carbon advances to a succeeding stage whereitis mixed with a lighter condensate and the mixture is subjected to alower temperature and pressure than the pressure and temperaturemaintained in the stage where the car.- bon was formed. The heavycondensates which are added to the residuum to make up a mixture forcirculation through a heating element serve to decrease the viscosity ofthe oil mixture, and since this condensate has all been vaporized in aprior heat treatment, it will be practically all cracked in its secondheat treatment.

Although the process of treating oil has been illustrated and describedas being carried out in three stages, it is to be understood that theinvention is not limited to a three-stage process. Some oils may beproperly treated in less than three stages and other oils may requiremore than a three-stage treatment. The number of stages to be used andthe specific temperatures and pressures in each stage depend entirelyupon the character of the oil being treated and the kind of nishedproduct to be obtained.

The method of separating the finished distillates from the vaporsremoved from the separators in the various converters is particularlyad- Vantageous in that a clean separation may be accurately made. Thevapors are scrubbed with condensates of vapors of the same general typeand any desired amount of condensate may be used for the scrubbingoperation. The temperature of the condensate used for scrubbing may beaccurately controlled by cooling the coils through Vthe vapors of eachchamber.

which they are circulated and in this way a large body of condensates ofany desired temperature may be circulated through the condenser. Thisscrubbing operation will prevent any of the higher fractions of oilgoing Vover into the finished distillate and will thus do away with thenecessity of through each of a series of separate heating zones' havingprogressively lower temperatures in the direction of advancement of theoil, passing the heated oil from each Zone to an unheated chamber-tocomplete the cracking reaction therein, separating a reflux condensatefromV the vapors from each chamber, withdrawing oil from each chamber,except the last, and mixing therewith Series 0f Separate heat CrackingStages having reflux condensate produced from the vapors from aSucceeding chamber,passing the resulting mix-V ture into the nextsucceeding heating zone, and separatinga gasoline distillate from vaporsof each chamber. o h

2. Arprorces's of Vcracking oil comprising circulating oil underpressure once only through each of a series of separate heating zones,maintaining a cracking temperature in each zone, successively reducingthe pressure on the oil in the direction of itsV advancement throughYthe heatingY zones, passing the heated oil from each zone to an unheatedchamber to complete the cracking reaction therein, separating a refluxcondensate fromV vapors from a succeeding chamber, passing theVresulting mixture into the next succeeding heating zone, and separatinga gasoline distillate from 3. A process of cracking oil, comprisingadvancing oil in a continuous path through a series of heating zones ofVsuccessively lower temperature in succession, maintaining a highpressure and cracking temperature in each Zone, separating refluxcondensates from vapors formed inthe heating zones, and supplying refluxcondensate from one Zone to oil passing through the next preceding zone.

4. A process of cracking oil, comprising advancing oil in a continuouspath through a series of heating Zones in succession, Ymaintaining saidzones at progressively'lower temperatures and pressures, separatingheavy condensates fromV vapors formed in the heating Zones, mixing aheavy condensate from each zone with the oil advancing through the nextpreceding zone, the h condensate from the-rst Zone being mixed with theoil passing through the last zone.

5. A process of cracking oilrcomprising advancing oil under pressure Yina continuous path through a series of separate cracking heating zonesmaintained at progressively decreasing temperatures, separatingcondensates from vapors formed in each heating zone and circulating saidcondensates through said heating Zones in a 'direction to subjectthem-to progressively increasing temperatures. Y

6. A processV of cracking oil comprising advancing oilV in a continuouspath through Va series of separate cracking heating zones maintained atprogressively decreasing temperatures and pressures in the direction ofthe advance of the oil, separating 'condensate from the vapors rvaporsformed in each stage, reducing the pressure of the separate vapors,collecting by 'condensation a heavy condensate and a gasoline distillatefrom the vapors of each stage, and passing the heavy condensatefrom-each stage for re-treatment in a stage of higher temperature.

V8. A continuous process of crackingroil'cornprising circulating oilunder pressure through a progressively lower temperatures and pressuresin the direction of advancement of the oil, removing residuum containingcarbon from the lowest temperature stage, separately condensing heavyand light distillates from the vapors formed in each stage underpressure lower than Y ithe pressures maintained in the respectivestages,

Vhigher pressurethan the pressure in the stage in which the vapor of theheavy condensate is formed.

' 9. A continuous process ofcracking oil com-Y prising passing oil underpressure through successive heat cracking stages of successivelydecreasing temperatures and pressures, the Voil residuumV from one stagepassing to a following stage, removing heavyY VcondensatesV from thevapors Tormedin each stage, introducing the rawoil in the stage havingthe highest temperature andrpressure, and introducing a high boilingpoint oil residuumto be cracked into the stage having the lowesttemperature and pressure,V and supplying heavy condensate from one stageto oil passing through the stage of the next higher temperature andpressure,V Y h 10. A process oi cracking oil in stages coin-V Yprisingvcirculating oil under pressure through a heating zone, separating bycondensation higher boiling point condensates from lower boiling'Y pointcondensates of the vapors formed in the said zone, separating a residuumoilV from theoil heated in said zone,and passing it'under pressure intoa second heating zone maintained at a lower temperature than said firstmentioned heating zone, passing said higher boiling point condensateinto oil passing through a third heating zone,V separating byYcondensation higher boiling point condensates from lower boiling pointcondensates from vapors formed in the Y Vsaid second heating Zone,separating a residuum oil under pressure from the oil-heated inthe saidsecond heating zone and passing it to said third heating zone, passingsaid second'V higher boiling point condensate under pressure into oilpassing throughY said Vrst heating` zone, condensing the vapor formed-inthe said third heating zone into'higher boiling and lower boiling pointcondensates, passing the oil residuum from the third zone out of the oilcracking system, and.

passing therhigher boiling point condensate Vfrom the third zone underpressure into oil passingV through the second heating Zone. v

il. The process of cracking oil, which comprises passing oil to becracked through a heating zone and then into a vapor separating zone inwhich vapors areseparated from unvaporized oil, passing unvaporized oilfrom said separating zone through a second heating Zone of lowertemperature .and then into a second vapor-separating` Zone, cooling .andcondensing portions of the vapors fromgsaid vapor-separating Zones inseparate refluxing zones, conducting uncondensed vapors from said refluxZones for final condensation and collection, and passing refluxcondensate from said reiiux zones into said first mentioned heating Zonefor retreatment.

12. The process of cracking oil which comprises passing oil once onlythrough each of a plurality f of heat-cracking Zones maintained atsuccessively lower cracking temperatures, separating vapors from the oilheated in each zone, condensing higher boiling constituents as a refluxcondensate from the vapors thus separated from the oil heated in eachzone, and passing the reflux condensate derived from each zone, exceptthe rst, through a heat-cracking Zone of higher temperature than thatmaintained in the zone from which the reux condensate was derived.

13. A hydrocarbon oil cracking process which comprises passing the oilserially through a plurality of interconnected reaction zones andmaintaining the oil under cracking conditions of temperature andpressure in each of saidr Zones, removing vapors from each of saidreaction Zones and introducing the same to independent dephlegmatingzones associated with the respective reaction zones, condensinginsuiiiciently cracked fractions of the vapors as refiux condensate insaid dephlegmating zones, passing reux condensate from a dephlegmatingzone associated with one of said reaction zones into a .precedingreaction zone in the series, and removing and condensing the vaporsuncondensed in said dephlegmating Zones. t

14. A hydrocarbon oil cracking process which comprises passing the oilserially through a plurality of interconnected reaction Zones andmaintaining th-e oil under cracking conditions of temperature andpressure in each of said zones, removing vapors from each of saidreaction Zones and introducing the same to independent dephlegmatingZones associated with the respective reaction zones, condensinginsufliciently cracked fractions of the vapors as reux condensate insaid Adephlegmating zones, passing reflux condensate from each of saiddephlegmating zones except the one associated with the first reactionZone into the preceding reaction Zone of the series, and removing andcondensing the vapors uncondensed in said dephlegmating zones.

15. The process of cracking mineral oi1s,which comprises passing the oilto be cracked through a heating zone in which it is subjected to acracking temperature and then into a vapor separating zone in whichvapors are separated from the unvaporized oil, passing unvaporized oilfrom said separating zone through a second heating and cracking Zone oflower pressure than said rstmentioned heating Zone and then into asecond vapor separating zone, cooling and condensing portions of thevapors from said vapor separating zones to produce reflux condensate anduncondensed vapors, subjecting the uncondensed vapors to nalcondensation and collection, and passing reflux condensate produced bythe reflux condensation of vapors from said separating zones into saidrst-mentioned heating zone to be subjected to cracking conditions oftemperature and pressure.

16. The process of converting heavy mineral oil cracking stock intolower boiling point products of the type of gasoline, which comprisespassing an oil stock to be cracked in a confined stream of restrictedcross section in a high temperature cracking zone and therein heatingand cracking the oil at high temperature, separating the products ofsaid stream into vapors and unvaporiaed oil constituents in a separatingZone, passing the unvaporized oil constituents from said separating zoneata reduced pressure into a separate zone in which they are subjected toa lower cracking temperature than that of the oil in saidfirst-mentioned zone, removing the vapors produced in said lowerpressure and temcondensate therefrom, separately fractionating thevapors separated out in said separating Zone to produce refluxcondensate therefrom, passing reflux condensate from both fractionatingoperations into said high temperature cracking zone to be crackedtherein, and collecting the low boiling point gasoline-like productsfrom the fractionating operations.

l'l. A hydrocarbon oil cracking process which comprises passing adistillate oil serially through a plurality of interconnected crackingZones and maintaining the oil under cracking conditions of temperatureand pressure in each of said zones, maintaining progressively lowerpressures through the cracking Zones, removing vapors from each of thecracking Zones and introducing the same to independent dephlegmatingZones associated with the respective cracking zones, condensinginsulciently cracked fractions of the vapors as reux condensate in saiddephlegmating zones, passing reflux condensate from a dephlegmating zoneassociated with .the second of said cracking Zones into the firstcracking zone of the series to supply at least in part the distillate tobe cracked therein, and removing and condensing the vapors uncondensedin said dephlegmating zones.

18. The process of converting higher boiling point hydrocarbon oils intolower boiling point products of the type of gasoline, which comprisespassing a distillate oil through a high pressure heating and crackingZone to effect vaporization and cracking of the distillate oil therein,separating vapors from unvaporized oil constituents resulting from theheating and cracking of said distillate oil, fractionating the vaporsseparated from the cracking of the distillate oil in said high pressureheating and cracking zone to produce a reflux condensate and an overheadvapor containing gasoline constituents, passing the unvaporized oilconstituents from the vhigh pressure cracking zone into a second lowerpressure cracking zone in which the unvaporized oil constituents areheated and subjected to cracking conditions, separating vapors andunvaporized residue from the cracking of said unvaporized oilconstituents and fractionating the Vresulting vapors to produce a refluxcondensate and an overhead vapor containing gasoline constituents, andpassing said refiux condensates into said vhigh pressure cracking Zoneto supply f y at least in part the distillate to be cracked therein.

CECIL E. BEATIE.

Yperni-ure zone and fractionating a heavy reux

